1. Field Of The Invention
The present invention relates to an automatic transmission primarily intended for motor vehicle use, and more particularly to a method of determining and controlling the frictional engagement or lock-up between a vehicle engine and a torque converter in a transmission that is controlled electronically and hydraulically.
2. Description Of Related Art
Generally speaking, land vehicles require three basic components These components comprise a power plant (such as an internal combustion engine) a power train and wheels. The internal combustion engine produces force by the conversion of the chemical energy in a liquid fuel into the mechanical energy of motion (kinetic energy). The function of the power train is to transmit this resultant force to the wheels to provide movement of the vehicle.
The power train's main component is typically referred to as the "transmission". Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle The vehicle's transmission is also capable of controlling the direction of rotation being applied to the wheels, so that the vehicle may be driven both forward and backward.
A conventional transmission includes a hydrodynamic torque converter to transfer engine torque from the engine crankshaft to a rotatable input member of the transmission through fluid-flow forces. The transmission also includes frictional units which couple the rotating input member to one or more members of a planetary gearset. Other frictional units, typically referred to as brakes, hold members of the planetary gearset stationary during flow of power. These frictional units are usually brake clutch assemblies or band brakes. The drive clutch assemblies can couple the rotating input member of the transmission to the desired elements of the planetary gearsets, while the brakes hold elements of these gearsets stationary. Such transmission systems also typically provide for one or more planetary gearsets in order to provide various ratios of torque and to ensure that the available torque and the respective tractive power demand are matched to each other.
Transmissions are generally referred to as manually actuated or automatic transmissions. Manual transmissions generally include mechanical mechanisms for coupling rotating gears to produce different ratio outputs to the drive wheels.
Automatic transmissions are designed to take automatic control of the frictional units, gear ratio selection and gear shifting. A thorough description of general automatic transmission design principals may be found in "Fundamentals of Automatic Transmissions and Transaxles," Chrysler Corporation Training Manual No. TM-508A. Additional descriptions of automatic transmissions may be found in U.S. Pat. No. 3,631,744, entitled "Hydromatic Transmission," issued Jan. 4, 1972 to Blomquist et al., and U.S. Pat. No. 4,289,048, entitled "Lock-up System for Torque Converter," issued on Sept. 15, 1981 to Mikel. et al. Each of these patents is hereby incorporated by reference.
In general, the major components featured in such an automatic transmission are: a torque converter as above-mentioned; fluid pressure-operated multi-plate drive or brake clutches and/or brake bands which are connected to the individual elements of the planetary gearsets in order to perform gear shifts without interrupting the tractive power; one-way clutches in conjunction with the frictional units for optimization of power shifts., and transmission controls such as valves for applying and releasing elements to shift the gears (instant of shifting), for enabling power shifting, and for choosing the proper gear (shift point control), dependent on shift-program selection by the driver (selector lever), accelerator position, the engine condition and vehicle speed.
The control system of the automatic transmission is typically hydraulically operated through the use of several valves to direct and regulate the supply of pressure. This hydraulic pressure control will cause either the actuation or deactuation of the respective frictional units for effecting gear changes in the transmission. The valves used in the hydraulic control circuit typically comprise spring-biased spool valves, spring-biased accumulators and ball check valves. Since many of these valves rely upon springs to provide a predetermined amount of force, it will be appreciated that each transmission design represents a finely tuned arrangement of interdependent valve components. While this type of transmission control system has worked well over the years, it does have its limitations. For example, such hydraulically controlled transmissions are generally limited to one or a very small number of engines and vehicle designs. Therefore, considerable cost is incurred by an automobile manufacturer to design, test, build, inventory and repair several different transmission units in order to provide an acceptable broad model line for consumers.
Additionally, it should be appreciated that such hydraulically controlled transmission systems cannot readily adjust themselves in the field to compensate for varying conditions such as normal wear on the components, temperature swings and changes in engine performance over time. While each transmission is designed to operate most efficiently within certain specific tolerances, typical hydraulic control systems are incapable of taking self-corrective action on their own to maintain operation of the transmission at peak efficiency.
However, in recent years, a more advanced form of transmission control system has been proposed, which would offer the possibility of enabling the transmission to adapt itself to changing conditions In this regard, U.S Pat. No. 3,956,947, issued on May 18, 1976 to Leising, et al., which is hereby incorporated by reference, sets forth a fundamental development in this field. Specifically, this patent discloses an automatic transmission design which features an "adaptive" control system that includes electrically operated solenoid-actuated valves for controlling certain fluid pressures. In accordance with this electric/hydraulic control system, the automatic transmission would be "responsive" to an acceleration factor for controlling the output torque of the transmission during a shift from one ratio of rotation (between the input and output shafts of the transmission) to another. Specifically, the operation of the solenoid-actuated valves would cause a rotational speed versus time curve of a sensed rotational component of the transmission to substantially follow along a predetermined path during shifting.
Although the idea of locking up the torque converter has been around for many years, few transmissions incorporated this feature before the fuel economy crunch of the 70's, because the fuel economy benefit of eliminating torque converter slip was not worth the driveability penalty that invariably resulted from eliminating the torque converter's damping effect Until recently, all torque converter lock-up was of the full lock-up variety, i.e., the lock-up clutch would fully engage and prevent any slip. Engine torsional vibrations would mostly be absorbed in damper springs located between the lock-up clutch and the turbine hub (transmission input). The lower limit for engine r p.m. depended on damper rate, number of cylinders, etc.; below this limit, high-frequency vibrations ("torsionals") made lock-up operation objectionable. In some cases, however, lower-frequency disturbances, e.g., surge or bucking, raised this limit.
An alternative to this is partial lock-up, a.k.a. controlled slight slippage of the lock-up clutch, which is disclosed in U.S. Pat. No. 4,468,988, issued Sept. 4, 1984 to Hiramatsu. No damper is necessary with this approach; lock-up clutch capacity is modulated to control lock-up clutch slip at some desired value, perhaps 50 r.p.m. The engine's torsionals go to its own inertia, resulting in an engine speed variation of perhaps .+-.30 r.p.m., so the clutch slips continuously; thus, the input torque to the transmission equals clutch capacity.
The disadvantages of the above patent include: slight fuel economy penalty versus full lock-up because of the slight slip (though full lock-up can still be used at higher r.p.m.); and the possibility of driveability problems due either to control system instability or control system amplification of engine torque instability.
3. Objects Of The Present Invention
It is one of the principal objects of the present invention to provide a significantly advanced electronically controlled transmission which is fully adaptive. By fully adaptive, it is meant that substantially all shifts are made using closed-loop control (i.e., control based on feedback). In particular, the control is closed loop on speed, speed ratio, or slip speed of either N.sub.t (turbine of the torque converter) and N.sub.e (engine) or a combination of N.sub.t and N.sub.o (output) which will provide the speed ratio or slip speed. This transmission control is also capable of "learning" from past experience and making appropriate adjustments on that basis.
Another object of the present invention is to provide an automatic transmission in which the shift quality is maintained approximately uniform regardless of the engine size, within engine performance variations or component condition (i.e. the transmission control system will adapt to changes in engine performance or in the condition of the various frictional units of the transmission).
It is a more specific object of the present invention to provide a method of determining and controlling a lock-up mode of operation of the torque converter to reduce the rotational speed difference between the torque converter and the vehicle engine.
It is an additional object of the present invention to provide full lock-up of the torque converter in a non-top gear of the transmission (i.e. third gear in a four speed transmission).
This application is one of several applications filed on the same date, all commonly assigned and having similar Specification and Drawings, these applications being identified below.
______________________________________ U.S. Ser. No. Title ______________________________________ 187,772 AN ELECTRONICALLY-CONTROLLED, ADAPTIVE AUTOMATIC TRANSMISSION SYSTEM 187,751 AUTOMATIC FOUR-SPEED TRANSMISSION 189,493 PUSH/PULL CLUTCH APPLY PISTON OF AN AUTOMATIC TRANSMISSION 187,781 SHARED REACTION PLATES BETWEEN CLUTCH ASSEMBLIES IN AN AUTOMATIC TRANSMISSION 189,492 CLUTCH REACTION AND PRESSURE PLATES IN AN AUTOMATIC TRANS- MISSION 188,602 BLEEDER BALL CHECK VALVES IN AN AUTOMATIC TRANSMISSION 188,610 PRESSURE BALANCED PISTONS IN AN AUTOMATIC TRANSMISSION 189,494 DOUBLE-ACTING SPRING IN AN AUTOMATIC TRANSMISSION 188,613 PARK LOCKING MECHANISM FOR AN AUTOMATIC TRANSMISSION 187,770 SOLENOID-ACTUATED VALVE ARRANGE- MENT OF AN AUTOMATIC TRANS- MISSION SYSTEM 187,796 RECIPROCATING VALVES IN A FLUID SYSTEM OF AN AUTOMATIC TRANSMISSION 187,705 VENT RESERVOIR IN A FLUID SYSTEM OF AN AUTOMATIC TRANSMISSION 188,592 FLUID ACTUATED SWITCH VALVE IN AN AUTOMATIC TRANSMISSION 188,598 DIRECT-ACTING, NON-CLOSE CLEAR- ANCE SOLENOID-ACTUATED VALVES 188,618 NOISE CONTROL DEVICE FOR A SOLENOID-ACTUATED VALVE 188,605 FLUID ACTUATED PRESSURE SWITCH FOR AN AUTOMATIC TRANSMISSION 187,210 METHOD OF APPLYING REVERSE GEAR OF AN AUTOMATIC TRANSMISSION 187,672 TORQUE CONVERTER CONTROL VALVE IN A FLUID SYSTEM OF AN AUTOMATIC TRANSMISSION 187,120 CAM-CONTROLLED MANUAL VALVE IN AN AUTOMATIC TRANSMISSION 187,181 FLUID SWITCHING MANUALLY BETWEEN VALVES IN AN AUTOMATIC TRANSMISSION 187,704 METHOD OF OPERATING AN ELEC- TRONIC AUTOMATIC TRANS- MISSION SYSTEM 188,020 METHOD OF SHIFT SELECTION IN AN ELECTRONIC AUTOMATIC TRANS- MISSION SYSTEM 187,991 METHOD OF UNIVERSALLY ORGANIZING SHIFTS FOR AN ELECTRONIC AUTO- MATIC TRANSMISSION SYSTEM 188,617 METHOD OF ADAPTIVELY IDLING AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 189,553 METHOD OF DETERMINING THE DRIVER SELECTED OPERATING MODE OF AN AUTOMATIC TRANSMISSION SYSTEM 188,615 METHOD OF DETERMINING THE SHIFT LEVER POSITION OF AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,594 METHOD OF DETERMINING THE ACCELERATION OF A TURBINE IN AN AUTOMATIC TRANSMISSION 187,771 METHOD OF DETERMINING THE FLUID TEMPERATURE OF AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,607 METHOD OF DETERMINING THE CONTINUITY OF SOLENOIDS IN AN ELECTRONIC AUTOMATIC TRANS- MISSION SYSTEM 189,579 METHOD OF DETERMINING THE THROTTLE ANGLE POSITION FOR AN ELECTRONIC AUTOMATIC TRANS- MISSION SYSTEM 188,604 METHOD OF CONTROLLING THE SPEED CHANGE OF A KICKDOWN SHIFT FOR AN ELECTRONIC AUTOMATIC TRANS- MISSION SYSTEM 188,591 METHOD OF CONTROLLING THE APPLY ELEMENT DURING A KICKDOWN SHIFT FOR ELECTRONIC AUTOMATIC TRANS- MISSION SYSTEM 188,608 METHOD OF CALCULATING TORQUE FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 187,150 METHOD OF LEARNING FOR ADAP- TIVELY CONTROLLING AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,595 METHOD OF ACCUMULATOR CONTROL FOR A FRICTION ELEMENT IN AN ELEC- TRONIC AUTOMATIC TRANSMISSION SYSTEM 188,599 METHOD OF ADAPTIVELY SCHEDULING A SHIFT FOR AN ELECTRONIC AUTO- MATIC TRANSMISSION SYSTEM 188,601 METHOD OF SHIFT CONTROL DURING A COASTDOWN SHIFT FOR AN ELEC- TRONIC AUTOMATIC TRANSMISSION SYSTEM 188,620 METHOD OF TORQUE PHASE SHIFT CONTROL FOR AN ELECTRONIC AUTO- MATIC TRANSMISSION 188,596 METHOD OF DIAGNOSTIC PROTECTION FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,597 METHOD OF STALL TORQUE MANAGE- MENT FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,606 METHOD OF SHIFT TORQUE MANAGE- MENT FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,616 ELECTRONIC CONTROLLER FOR AN AUTOMATIC TRANSMISSION 188,600 DUAL REGULATOR FOR REDUCING SYSTEM CURRENT DURING AT LEAST ONE MODE OF OPERATION 188,619 UTILIZATION OF A RESET OUTPUT OF A REGULATOR AS A SYSTEM LOW- VOLTAGE INHIBIT 188,593 THE USE OF DIODES IN AN INPUT CIRCUIT TO TAKE ADVANTAGE OF AN ACTIVE PULL-DOWN NETWORK PRO- VIDED IN A DUAL REGULATOR 188,609 SHUTDOWN RELAY DRIVER CIRCUIT 188,614 CIRCUIT FOR DETERMINING THE CRANK POSITION OF AN IGNITION SWITCH BY SENSING THE VOLTAGE ACROSS THE STARTER RELAY CONTROL AND HOLD- ING AN ELECTRONIC DEVICE IN A RE- SET CONDITION IN RESPONSE THERETO 188,612 THROTTLE POSITION SENSOR DATA SHARED BETWEEN CONTROLLER WITH DISSIMILAR GROUNDS 188,611 NEUTRAL START SWITCH TO SENSE SHIFT LEVER POSITION 188,981 OPEN LOOP CONTROL OF SOLENOID COIL DRIVER ______________________________________
Commonly assigned application Ser. No. 07/187,772, filed Apr. 29, 1988, now U.S. Pat. No. 4,875,391 has been printed in its entirety. The Figures and the entire Specification of that application are specifically incorporated by reference. For a description of the above copending applications, reference is made to the above mentioned U.S. Pat. No. 4,875,391.